Camera doesnt follow ball in tube (Blender Game Engine)
I'll try to address at least something:

1) Your "tube" material has "backface" enabled, thus now you can't see it from the inside, because  tube's normals are pointing outside. Try to remove backface OR leave backface, but invert normals (in this way you can also see through the tube when looking the whole tube path from outside, to get a bird's eye view, which helps to spot how is working well and where not...

2) the current camera parenting isn't working well: moving the ball (pressing S) it goes behind it at the beginning, but then it goes around it (and something goes out of the tube), then also in front of the ball... I think you should somehow set the position  of the camera to be always behind the ball along the ball direction axis... I don't know how, unfortunately.